Telephone system



Dec. 1, 1936. Q E ARE 2,062,444

' TELEPHONE SYSTEM Filed March 15, 1935 INVENTOR O CESAREO ATTORNEYPatented Dec. 1, 1936 UNITED STATES PATENT OFFICE TELEPHONE SYSTEMApplication March 13, 1935, Serial No. 10,779

9 Claims.

This invention relates to telephone systems and particularly toimprovements in telephone systems of the coin controlled type.

In coin controlled telephone systems in use today the coin controlmagnet located at a pay station is designed to operate on a voltage ofapproximately sixty volts, which is the potential obtained at the coinbox station from the coincollect or coin-refund battery located at thecen- 10 tral office and to non-operate at a potential of approximatelyforty volts, which is the potential obtained during a call from a flowof current to ground through the magnet from the talking battery at thecentral oflice. This comparatively high non-operate condition which isimposed on the magnet to prevent its false operation requires aninsensitive adjustment on the magnet which limits the line loop overwhich the coin collector may be operated.

It is the object of this invention to increase the loop range over whichcoin collection in a telephone system is permissible.

This object is attained in accordance with a feature of the invention byremoving the nonoperate condition heretofore imposed on the coin magnetwhich constitutes a part of a telephone coin collector. This is effectedby the use of a combination of polarized cold cathode gas-filled tubeswhich present an open circuit to ground from the central ofiice batteryand render it possible to operate the coin collector with a singlemagnet coil, thereby extending the line loop range by one thousand ohms,or by double the resistance of a single coil of the coin control magnet,it being necessary, heretofore, to operate the coin control magnet byway of its two coils, each coil having a resistance of approximatelyfive hundred ohms.

The invention will be readily understood from the following' detaileddescription made with reference to the accompanying drawing in which,

Fig. 1 shows a calling subscribers line provided with coin box equipmentand the gas-filled tube circuit arrangement of this invention as- 5sociated therewith, a coin-trunk circuit, a line finder through whichthe calling subscribers line has access to the trunk, a selectorassociated with the trunk, a connector and a called subscribers line towhich a connection may be extended 5 through the selector and connectorfrom the calling subscribers line, and

Fig. 2 shows a modified form of the invention in which the functionsperformed by the tube relays of Fig. 1 are performed by the coin col-55.1ector.

(Cl. 179-63) i In the several figures, only those parts of the systemand apparatus which are necessary for a complete understanding of theinvention have been shown in detail.

It is believed that the invention will be best 5 understood from adescription of the manner in which a call originating at a prepaymentstation is extended to a called station and the manner in which the coincollector mechanism functions to either collect or refund the coins de-10 posited in the coin box at the calling station depending upon whetheror not the call has been successfully completed.

Assuming therefore, that a subscriber at station 2 desires to be placedin telephone commu- 15 nication with a subscriber at'station 3, he willremove the receiver from its switchhook whereupon the line finder 4 isactuated in a well-known manner to seize the calling line and connect itwith the coin-trunk circuit CT. As the circuit 20 for extending theconnection to the trunk forms no part of this invention, no descriptionwill bemade thereof. g 7

It will be assumed therefore, that upon the establishment of thisconnection a circuit will be completed through the calling subscribersloop for the operation of the usual pulsing relay 5 of the selector 6.This circuit may be traced as follows: grounded battery, left-handwinding of relay 5, upper make-before-break contacts of relay 1, windingof polarized relay 8, back contact and upper armature of relay 9, tipconductor of trunk CT, through the line finder 4 and the loop closedthrough the subscribers telephone set at station 2, ring conductor ofthe call- 35 ing line, through the line finder 4, lower armature andback contact of relay 9, outer lower make-before-break contacts of relay1, to ground through the right-hand winding of relay 5. Means in theselector 6, which has not been 40 shown, causes, through the operationof relay 5, the transmission of a dial tone over the tip conductor tothe calling subscriber to indicate that the circuits are now incondition for transmis sion of dial pulses.

The calling subscriber after having removed the receiver from theswitchhook deposits a coin ID in the coin box equipment indicated by thenumeral I l, and upon hearing the dial tone proceeds to actuate hiscalling dial in accordance with the digits of the number correspondingto the called station 3. It will be noted that the deposit of coin H1 inthe coin box opens the shunt circuit around the dial pulsing contactswhich is normally maintained closed by the-coin box contacts l3. It isapparent that unless a coin is deposited in the coin box the dial I4cannot be effectively operated.

The calling subscriber now dials the number of the desired subscriberand pulsing relays 5 and 6| respond to extend the connection. The pulsesof the first digit operate the selector 6 to select the connector [5which in 'turnis operated by pulses of the second and third digits toselect the desired subscriber at station 3. Seizure of connector l5causes relay 6| to operate over the closed loop of the callingsubscribers line and establish an obvious circuit for slow-to-releaserelay 62 which connects ground to the'sleeve terminal of selector 6marking this switch busy and holding it operated. The connector onfinding the line of the desired subscriber, is operated in thewell-known manner totransmit ringing current over the line to signal thecalled subscriber. As stated, the automatic switches 6 and I5 may be ofany well-known design and their operations need not be described indetail. However, when the called subscriber removes the receiver fromthe switchhook an. obvious circuit is established for relay 60 whichoperates to reverse the direction of current flow in the loop circuit ofsubscribers station 2 which is in series with impulse relay 6|. It issufficient to state that when the called subscriber atstation 3 respondsto the signal by removing the receiver from its switchhook, current overthe tip and ring conductors of the trunk CT is reversed.

This reversal of current causes the operation of polarized relay 8. Itshouldalso be mentioned at this time that after the seizure of theselector 6, the ground potential applied to the sleeve terminal thereofcauses the operation of relay I6. This relay closes an obvious circuitfor the operation of relay I! which, in: operating, closes a connectionto ground for the sleeve conductor l8 of the line finder 4 to maintainthe line finder busy, as is well known in the art.

Relay 8 in operating, closes a circuit for the operation of relay 1extending from grounded battery, winding of relay 1, back contact andarmature of relay-I9, conductor 20, front contact and armature ofrelay 8to the above-mentioned ground on the sleeve conductor of the line finder4 appliedat the upper inner armature and front contact of relay ll.Relay in operating, provides a locking circuit for itself through itsinner lower armature and front contact to ground on the sleeve conductorl8 independent of the original circuit through the front contact andarmature of relay 8. Relay 1, operated, also reverses the tip and ringconductors towards the calling subscribers line to cause the release ofrelay 8 and vfor other purposes of no importance with the presentinvention. Relay 1 also establishes a circuit for the operation of relayl9 extending from grounded battery, winding of relay l9, double frontcontacts and inner lower armature of relay 1 to ground on the sleeveconductor I8. This relay in operating, opens the original circuit forrelay 1. v

It willbe noted that when relay 8 first operated, a circuit'for theoperation of relay 2| was established extending from grounded battery,winding and normal make-before-break contacts of relay 2|, conductor2||,'frontcontact and armature ofrelay 8 to ground on the sleeveconductor I8. Relay -2| locks directly to ground on the sleeveconductorl8 and accordingly remains operatedwhen-relay 8 releases as justdescribed.

It-willnowbe assumed thatthe period of conversation between thesubscribers at stations 2 and 3 has ended and the calling party hangs uphis receiver. This causes the selector 6 and connector l5 to be releasedin the well-known manner, with the result that relays 60, 6|, and 62 andconsequently relay l6 restore to normal. Relay IB in releasing itsarmature closes a circuit for the operation of relay 9 extending fromgrounded battery, winding of relay 9, armature and right-hand contact ofslow-to-release relay ll, to ground on the back contact and armatureofrelay IB. Relay 9 in operating establishes, at its upper armature andfront contact, a circuit extending from the coin collect battery 22,front contact and left-hand armature of relay 2|, conductor 23, frontcontact and upper armature of relay 9, tip conductor of trunk CT, tipterminals of line finder 4, tip conductor of the line of station 2,conductor 24, to the anode of gas-filled tube 25. The positive potentialof battery 22 is also applied to cathode 26 by way of resistance 27.This potential is also applied to the cathode 28 of tube 29 but is ofsuch a polarity as to have no efiect on the tube 29.

It will be noted that the cathode 30 of tube 25 is connected to groundpotential by way of the Winding of relay 3| conductor-32, left-hand coil33 of the coin collector l. to ground at the coin contacts 34. Thepotential across the cathodes 26 and 33 of tube 35 is sufiiciently greatto cause the tube to break down across the gap between the two cathodes.This preliminary breakdown, or flashing, of the tube 25 occurs betweenthe cathodes 26and 30 and is thereafter maintained between the anode andcathode 30. Due to the breakdown of the tube 25, the circuit previouslytraced from battery 22. tothe anode of tube 25 is completed to ground atthe coin contact 34 by way of relay 3| and coil 33 of the collectorRelay 3|, which .is highly sensitive, operates in this circuitandestablishes a locking circuit for itself which extends from thetipconductor of trunk CT, conductor 24, conductor 35, conductor 36,armature and front contactof relay 3|, winding of relay 3 conductor 32,coil 33 to ground at contacts 34. It will be noted that the operation ofrelay 3| causes the tube 25 to be short-circuited, thereby effecting alow resistance path for the operation of coil 33 of collector II inseries with relay 3|. The coil 33 operates in this circuit causing thecoin l0 deposited in the coin box to b collected.

Thetube 25 being short-circuited becomes deenergized and resumes-itsnormal condition.

It will be noted that relay 'I'! is slow-to-release so it willremainoperated for a sufficient period of time to permit relayB to operateafter relay i6 is released, the time of operation of relay 9 beingdetermined by the slow release characteristics of relay ll. It shouldalso be noted that. when relay l1 operated, ground potential was appliedat its left-hand armature and front contact to the sleeve conductor l8of the line finder 4. This is for the purpose ofmaintaining the linefinder 4 operated afterthe calling subscriber has returned his receiverto the switchhook which would ordinarily cause the line finder torelease. The line finder must be maintained operated long enough topermit the collect battery current to pass over the subscribers line tooperate the coin equipment. "After an interval of time relay |l restoresto normal removing the ground from the sleeve of line finder 4 whichthereupon is released and the circuit from collect battery 22 to thecoil 33 is broken whereupon relay 3| and the magnet coil 33 aredeenergized.

In the event that the called subscriber at station 3 does not answer thecall or the calling sub-- 'scriber at station 2 abandons the call beforethe called subscriber answers, the coin magnet coil 38 becomes energizedto cause the coin collector H to function and refund the coins depositedtherein. In this event, relay 8 will not be operated, thus preventingthe operation of relays 2i, 1, and I9. However, as relay I6 is operated,the operation of relay ll takes place. When therefore, the calling partyreleases the connection and relay I6 is released, current from therefund battery 40 will be transmitted through the back contact andleft-hand armature of relay 2|, through the front contact and upperarmature of relay 9 to the tip conductor of the trunk CT to actuate thecoin collector ll to refund the coins deposited therein.

Current from the negative battery 40 being applied to the tip conductorof trunk CT passes through the line finder 4 tothe tip conductor of theline of station 2, conductor 24 to the anode of tube 25 and also to thecathode 28 of tube 29. The direction of current in this case is suchhowever as to have no effect on the tube 25. Tube 29, however, doesbreak down across the cathodes 28 and 4|, the latter being connected toground potential by way of resistance 42, winding of relay 43, conductor44, coil 38 of collector II to ground at the coin contacts 34. The tube29 accordingly functions in a manner similar to that already describedin connection with tube 25 to cause the energization of coil 38 whichresults in the operation of the collector II to refund the coinsdeposited therein.

In Fig. 2, which discloses a modified form of this invention, thesensitive relays 3| and 43 of Fig. 1 are omitted and the functionsperformed by these relays in the system of Fig. 1 are now performed bythe coin control magnet itself.

The same numerals have been used in Fig; 2 to identify correspondingelements of Fig. 1. It is believed unnecessary to enter into a detaileddescription of the arrangement shown in Fig. 2 as it would entail, to amajor extent, a repetition of the description made in connection withFig. 1. However, a brief reference to the points of distinction betweenthe two arrangements will be made.

It will be noted that contacts 50 and 5! have been added to the coincontrol magnet and correspond to the front contacts of relays 3i and 43,respectively, of Fig. 1. When tube 25 flashes, the coil 33 receivessufficient current to partially operate and cause the closure ofcont-act 50 which short-circuits the tube 25 by way of conductor 55. Thecoil 33 now becomes fully energized and locks operated in the lowresistance path including the tip conductor of trunk CT. This circuitextends from ground on the coin contacts 34, conductor 56, magnet coil33, contact 50 and armature of coin collector ll, conductor 55, which isconductively associated with the armature of the coin collector,conductor 35, conductor 24 to the tip conductor of the trunk CT. Theenergization of coil 38 and the consequent closure of contact 5|, inlike manner, results in the locking of coil 38 to the tip conductor oftrunk CT and the short circuiting of tube 39.

What is claimed is:

1. In a telephone system, a telephone line, a coin collector, a centralofiice, a source of current at said central omce, means for connectingsaid source of current to said line, and a device normally maintainingan open circuit between said line and said coin collector and adapted toclose a circuit between said line and said collector when said source ofcurrent is connected to said line whereupon said collector operates oncurrent from said source.

2. In a telephone system, a telephone line, a coin collector, a centraloffice, a source of current at said central ofiice, means for connectingsaid source of current to said line, and a gaseous conductor normallymaintaining an open circuit between said line and said collector andadapted to complete a connection between said line and said collectorwhen said source of current is connected to said line whereupon saidcollector operates on current from said source.

3. In a telephone system, a telephone line, a coin collector, operatingmeans for said collector including a coil of an electromagnet, a centraloifice, a source of current at said central ofiice of a certain voltage,a second source of current at said central office of a voltage differentthan that of said first source, means for connecting said currentsources to said line, and means interposed between said coin collectorand said line for completing a circuit from said line to said coil whensaid first source of current is connected to said line and formaintaining an open circuit between said coil and said second source ofcurrent when the latter is connected to said line.

4. In a telephone system, a telephone line, a coin collector, operatingmeans for said collector including a magnet, a central ofiice, sourcesof current of difierent voltages at said central ofiice, means forconnecting said sources to said line, and a voltage discriminatingdevice interposed between said line and said collector for renderingsaid magnet operative when one of said sources of current is connectedto said line and for preventing the operation of said magnet whenanother of said sources of current is connected to said line. I

5. In a telephone system, a line terminating at a central ofiice, a coincollector normally on open circuit with respect to said line, a sourceof current of a certain voltage at said central office, a second sourceof current at the central ofiice of a voltage lower than that of saidfirst source, voltage discriminating means connected between said lineand said collector, said means being unresponsive to the voltage of saidsecond source and responsive to the voltage of said first source forcompleting a circuit from said line to said collector and causing theoperation of said collector, and means at the central ofiice forconnecting said current sources to said line.

6. In a telephone system, a telephone line, a coin collector normally onopen circuit with respect to said line, a central office, a source ofcurrent at said central office, means for connecting said source ofcurrent to said line, a gaseous conductor interposed between said lineand said collector and responsive to the voltage of said I centraloffice, a gaseous conductor interposed between said line and saidcollector and having an anode and a cathode, means at said centraloflice for impressing the voltage of said source on the anode of saidgaseous conductor to cause said conductor to break down and complete thecircuit between said line and said collector by way of the anode-cathodecircuit of said conductor, and means in series with the cathode of saidconductor operating as a result of the completion of the anode-cathodecircuit of said gaseous conductor for short-circuiting said gaseousconductor and locking said collector to said line whereupon saidcollector operates on current from said source independently of saidgaseous conductor.

8. In a telephone system, a line terminating at a central ofiice, a coincollector including two independent operating coils, a source of currentat said central ofiice, a second source of current at said centralofiice, said sources being of the same voltage and different polarities,a pair of polarized gas-filled tubes interposed between said line andsaid collector, each tube having an element thereof in series with adifierent coil of said collector, means for connecting said first sourceto said line whereupon one of said tubes functions to complete anoperating circuit to its respective collector coil to operate saidcollector in a certain manner, and means for connecting said secondsource to said line whereupon the other of said tubes functions tocomplete an operating circuit to its respective collector coil tooperate said collector in a dififerent manner.

9. In a telephone system, a telephone line, a coin collector normally onopen circuit with respect to said line, a central office, a source ofcurrent at said central oifice, means for connecting said source ofcurrent to said line, a gaseous conductor interposed between said lineand said collector and responsive to the voltage of said source forcompleting the connection between said line and said collector to effectthe operation of said collector, and means controlled by said collectorand effective upon the operation thereof for short-circuiting saidgaseous conductor and locking itself to said line independently of saidgaseous conductor.

ORFEO CESAREO.

